Spinal Muscular Atrophy (SIVIA) is a devastating inherited neurodegenerative disease causing progressive loss of motor functions due to malfunction of neuromuscular junctions (NMJs) and eventual loss of motor neurons. SMA is caused by loss of Survival of Motor Neuron (SMN1), a component of the nuclear gemin complex which is thought to mediate assembly and transport of snRNP complexes and thus control the synthesis and delivery of key synaptic proteins. However, the identity and function of relevant SMN target genes and the precise molecular role of SMN at the NMJ remain largely a mystery. The proposed project focus will be to use simple genetic model systems to dissect the mechanism(s) by which SMN controls synaptic form and function, and thus identify likely targets for interventions to attenuate SMA in mammalian models or human patients. We will be using genetic approaches in Drosophila to identify functional modifiers of SMN mutations and will study them in both Drosophila as well as C.elegans (Artavanis-Tsakonas, van Vactor and Hart Laboratories). Mammalian cell assays (Rubin laboratory) will extend and corroborate the studies in invertebrates while possible functional relationships and pharmacological interventions identified in mammalian cells will be tested using the sophisticated genetic tools that C elegans and Drosophila offer. Each system has unique experimental advantages and the integration of the proposed analysis across vertebrates and invertebrates offers exceptional promise for an in depth understanding of SMN biology and pathology while, importantly, it carries the promise of identifying novel therapeutic avenues.